The problem of cross-staining between cotton fabrics during laundering and processing is a significant household and textile problem. Cross-staining relates to the transferring of dye that may occur between fabrics under either wet or dry conditions while fabrics are being manufactured, processed or laundered. Television commercials are aired daily for expensive detergents meant to minimize cross-staining. In fact, much advertising and product manufacturing are devoted to this common annoyance. The detergents that advertise colorfastness are designed to approach the problem of cross-staining through the use of dye antiredeposition agents that are incorporated into their formulas. These antiredeposition agents, however, add expense to the detergents and are not fully effective in preventing cross-staining. Thus, a method of preventing dye transfer without relying on the use of detergents would prove to be both practical and economical.
The dye transfer between cellulosic fabrics, such as cotton fabrics, occurs when fabrics are laundered or processed in the same bath. Dye transfer occurs because cellulosic fibers have a mild attraction for anionic classes of dyes, which are the majority of the dyes now employed to dye cotton and other cellulosic fabrics and blends. Dyes are made to be anionic or negatively charged so that they will benefit from water solubility. Such classes of dyes include reactives, directs, acids, and the like. A primary example of this dye transfer is the staining of the white pockets in blue jeans during garment manufacture and during laundering. The anionic leuco form of the indigo dyes in the blue jeans are absorbed by the undyed cotton fibers in the pockets because of their chemical attraction to one another.
An even more well-known example is the transfer of dyes between dark-colored garments and white or light-colored garments during the laundering process. The loosely-held anionic dyes in the fibers of the dark-colored garments stain the white or light-colored garments. This dye transfer may adversely affect white or light-colored garments. Similarly, striped or patterned garments containing both dark-colored fabric and white or light-colored fabric may experience bleeding of the dark-colored dyes on to the lighter portions because of the attraction of unfixed anionic dyes to the cellulosic fibers in the white or light-colored portions. Therefore, it is evident that weakening this attraction between the anionic dyes and the cotton fibers would provide a solution to the problem of dye transfer.
A need currently exists for a solution to the problem of dye transfer regarding cellulosic fabrics so that the needs for expensive detergents and other methods of colorfastness are eliminated. In particular, a need exists for a process that treats cellulosic fibers in order to permanently increase their anionic character so that these fibers are able to resist anionic dyes that cross stain fabrics. The present invention is directed to a process that meets the above described need.